I believe voice may be the most difficult instrument to teach as everything important happens internally and therefore cannot be observed. The other end of the spectrum could be piano or stringed instruments: difficult to play, yet everything, or nearly everything, important to basic technique can be observed. Performing on brass instruments is closer to the singing end of the spectrum: valve and slide technique, while important and visible, are not the crux of the matter.

One may observe great embouchures in action by watching the German Brass. Their videographer tends toward closeups that offer the opportunity to observe virtuoso performing in detail. The most startling aspect is the appearance that the performers seem to be doing nothing whatsoever: their embouchures seem immobile and mostly relaxed. The piccolo trumpet playing of Mathias Höffs is especially impressive. His playing seems effortless because one does not see any embouchure motion. He uses firm, frowning corners that never move to set an efficient aperture: all of the work is in the internal tongue dance.

Magnetic resonance imaging (MRI) technology offers new ways of viewing internal activity. Thevideo of Sarah Willis playing french horn while being observed via MRI scanning is some of the best 'internal' observation yet recorded--the importance of the tonguing for changing pitches cannot be overstated. Watching her tongue ascend until it appears tp be pressed against the roof of her mouth explains the secret of achieving the highest pitches.

Because the technique is mostly internal, great brass playing appears easy, almost magical. Brass playing is not literally effortless, but, an efficient embouchure can make it seem so. Firm, stable corners, with a slight frown and a flat chin are the hallmarks of an efficient embouchure. Exercises that help create such stable embouchures include free buzzing, mouthpiece buzzing, pitch bends, breath attacks and pedal tones. Special Studies by John Daniels offers a good approach to many of these techniques.